Mosquito Larvae Eradication

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QUESTION

What measures can be taken to eradicate mosquito larvae?

ANSWER

The main methods to control mosquito larval populations are by reducing areas available for adults to breed and also directly killing larvae. So, for example, adult mosquitoes need standing, stagnant water in order to lay their eggs. Getting rid of these sources of standing water, for example by filling in unwanted ditches and removing empty containers that can become filled with rainwater, therefore reduces the available breeding habitat for mosquitoes. Similarly, dripping a small amount of oil on top of standing water creates a thin film of oil over the surface of the water, preventing adults from laying eggs. In addition, the oil prevents the larvae from gaining access to air, suffocating them and killing them. There are other methods for killing larvae too. Directly spraying insecticides onto water is one method, but often not very specific, and can have a negative effect on other forms of aquatic life. One popular method for biocontrol is to introduce other animals which eat mosquito larvae, thus keeping numbers down. Examples include certain species of fish, as well as small crustaceans called copepods.

Malaria Eradication and Water Quality

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QUESTION:

How will the eradication process of the mosquito larva influence the quality of the water?

ANSWER:

That’s a very interesting question. The answer is that it depends a lot on the way in which the mosquito larva are controlled. The usual, traditional method is through the application of insecticides. Many of these are known to have severe negative effects on water quality, particularly through being non-selectively toxic and therefore killing lots of other aquatic life as well as the mosquitoes. Moreover, some are known for their effects on animals further up the foodchain; the most famous example of this being DDT, which was used to kill adult mosquitoes. It was discovered that this pesticide resulted in birds laying eggs that had very thin shells, preventing the chicks from hatching successfully. As such, it was banned in most developed countries. Modern insecticides used for mosquito larva reduction have been developed to target mosquitoes specifically; a popular one in the USA is methoprene, which interferes with the mosquitoes’ growth hormones, preventing development into adults. Microbial compounds, which are not dangerous to other organisms, are also sometimes used.

Another approach is through the use of natural enemies of the mosquito larvae, notably certain species of fish and dragonflies. These will eat mosquito larvae and pupae, thus naturally reducing numbers, and with little undue effect on water quality (although in some contexts, such as reservoir water, there may be concerns with stocking the water source with large numbers of fish).